This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Using a double blind, randomized crossover trial of coEnzyme Q10 (Q10) 100mg three times a day (tid), 200mg tid, or placebo for (four) 3 month treatment periods in 40 (8 extra participants will be recruited to account for dropouts, 32 subjects are expected to complete the protocol) subjects, we propose to assess the hypotheses that: 1. Q10 will improve overall subjective quality of life (QOL) in ill Gulf War Veterans (GWV), using a single item QOL measure. 2. Q10 will improve specific symptoms that dominate definitions of illness in GWV including fatigue, pain, and muscle strength. 3. Q10 will subjectively improve other symptoms reported to arise at elevated rates in GWV defined by responses on a symptom survey (e.g. headache, shortness of breath, sleep problems, gastrointestinal problems). 4. Effect modification: The magnitude of Q10 benefit may be influenced by baseline oxidative state, change in oxidation with Q10, and serum Q10 level;or by which symptoms a veteran has. 5. Dose response. We seek to assess whether higher dose Q10 provides greater (or the same, lesser) benefit;or does so selectively in individuals with more unfavorable baseline oxidation state;or individuals who require a higher dose to achieve the same change in Q10, e.g. due to impaired assimilation